21559813 has 16 divisors (see below), whose sum is σ = 25344000. Its totient is φ = 18128880.

The previous prime is 21559801. The next prime is 21559829. The reversal of 21559813 is 31895512.

It is not a de Polignac number, because 21559813 - 2⁵ = 21559781 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21559843) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7788 + ... + 10186.

It is an arithmetic number, because the mean of its divisors is an integer number (1584000).

Almost surely, 2^21559813 is an apocalyptic number.

It is an amenable number.

21559813 is a deficient number, since it is larger than the sum of its proper divisors (3784187).

21559813 is a wasteful number, since it uses less digits than its factorization.

21559813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2472.

The product of its digits is 10800, while the sum is 34.

The square root of 21559813 is about 4643.2545698034. The cubic root of 21559813 is about 278.3225084136.

The spelling of 21559813 in words is "twenty-one million, five hundred fifty-nine thousand, eight hundred thirteen".